PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Sperry Top Sider Women's Casual Classic Boat Shoes 6 M Pink and White Eyelet , Women’s Ladies New Flat Ankle Strap Toe Post Diamante Gladiator Summer Sandals , THEME WOMAN'S SANDALS SIZE 11W MUSTARD YELLOW BRAND NEWSAS BROWN LEATHER SLIP ONS DRESS WALKING COMFORT SHOES WOMEN'S Size 8.5 MNICE Women's Pliner Jrs Oliver Loafers Shoes Brown Leather-US 7.5 , New PUMA Shocking Pink Tekkies Jam Casual Shoes Women’s Size 7.5**Soft Style Valda Oxfords - Women's Size 8 M, Dark Grey PaisleyGRASSHOPPERS SHOES WOMENS SIZE 8 1/2 MPuma Fenty Rihanna Creeper Bow Espadrilles Platform D’orsay Oatmeal US 6.5 $180 , Merrell Primo Chill Slide Women's Size 7 Moc/Clogs Chocolate Brown SuedeKlogs Footwear Reyes Leather Slip On Sneakers, Women's Size 11M, Black/LunarVivienne Westwood Anglomania Melissa Black Space Love Ballet Flats Shoes Sz 6 37 , Aldo Black Leather Mules Wood Heels Clogs - U.S. Size Size 9 , Basket Surpiquée Montante Femme en Toile Fashion !Salomon Citycross ladies trail running shoes size 7Aerosoles Innovation Nubuck Tan Loafers Size 7New Balance 690 Women's Walking/Trail Running, Shoes/Sneakers Size 7B W690NL EUC , Teva Freewheel Washed Canvas Sneaker- Women's Size 11, Black/Grey , Nike Air Max Running Shoes White/Navy/Blue Women’s Size 6.5 , Merrell Running Shoes Green Leather Women5Medium (B, M)Nike Structure 13 Trail Running Shoes Athletic Sneakers 386408- 061 Gray Size 7 , Women's Ferragamo loafers 5.5 Be Novel In Design FlatsADIDAS GAZELLE GENUINE LOW SNEAKERS WOMEN SHOES BEIGE / WHITE BB5178 SIZE 9 NEW , Nike WMNS Roshe Two Print 2 women lifestyle sneakers NEW blue spark 844933-401VANS Old Skool Velvet Black Skate Shoe Women's Size 5.5 Mens Size 4Rottweiler Print Christmas Running Shoes For Women-Free ShippingSuperga Women's 2750 Fancotu Sneaker - Choose SZ/ColorSkechers Women's Go Walk Lite-15400 Wide Ballet FlatASICS GEL VENTURE 5 RUNNING TRAIL SHOES WOMENS SZ 11 GRAY PINK ATHLETIC EUCWomens Asics Size 7, New in Box, Pale Blue and Silver, Quickwalk 3 ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."